Citation Nr: A25035605 Decision Date: 04/17/25 Archive Date: 04/17/25 DOCKET NO. 240925-478451 DATE: April 17, 2025 REMANDED Entitlement to service connection for colon cancer is remanded. REASONS FOR REMAND The Veteran had active service in the United States Air Force from February 1961 to February 1981 with military occupation specialties (MOS) of Tactical Aircraft Maintenance and Operating Room Technician. His pertinent awards and decorations include the Vietnam Service Medal, Republic of Vietnam Gallantry Cross with Palm, Republic of Vietnam Campaign Medal, and the Air Force Longevity Service Ribbon with 4 Oak Leaf Clusters. This matter comes before the Board of Veterans' Appeals (Board) on appeal from a September 2023 rating decision issued by the Agency of Original Jurisdiction (AOJ), a Department of Veterans Affairs (VA) Regional Office (RO). In the September 25, 2024, VA Form 10182, Decision Review Request: Board Appeal (Notice of Disagreement), the Veteran elected the Hearing docket. A Board hearing was held on January 10, 2025, before the undersigned Veterans Law Judge. A transcript of that proceeding has been associated with the claims file. Consequently, the Board may only consider the evidence of record at the time of the September 2023 AOJ decision on appeal, as well as any evidence submitted by the Veteran [or representative] at the hearing or within 90 days following the hearing. 38 C.F.R. § 20.302(a). If evidence was submitted either (1) during the period after the AOJ issued the decision on appeal and prior to the Board hearing, or (2) more than 90 days following the hearing, the Board did not consider it in its decision. 38 C.F.R. §§ 20.300, 20.302(a), 20.801. However, because the Board is remanding the claim, any evidence the Board could not consider will be considered by the AOJ in the adjudication of the claim. 38 C.F.R. § 3.103(c)(2)(ii). Although the Board sincerely regrets the additional delay, remand is required to ensure that there is a complete record upon which to decide the issue so that the Veteran is afforded every possible consideration. This appeal has been prioritized on the docket due to advanced age. See 38 U.S.C. § 7107(b); 38 C.F.R. § 20.800(c). Entitlement to service connection for colon cancer is remanded. The Veteran contends that his colon cancer is related to toxic exposure during service, to include herbicide agents and other environmental hazards associated with his duties and service locations. Service connection may be granted for disability resulting from disease or injury incurred in or aggravated by active service. 38 U.S.C. §§ 1110, 1131, 5107; 38 C.F.R. § 3.303. The three-element test for service connection requires evidence of: (1) a current disability; (2) in-service incurrence or aggravation of a disease or injury; and (3) a causal relationship between the current disability and the in-service disease or injury. Shedden v. Principi, 381 F.3d 1163, 1166-67 (Fed. Cir. 2004). The first element of service connection is met. The Veteran has a current diagnosis of colon cancer. The second element of service connection is also met. VA regulations provide that a veteran who served in the Thailand at any United States or Royal Thai base from January 9, 1962, to June 30, 1976, shall be presumed to have been exposed to an herbicide agent during such service, without regard to where on the base the veteran was located or what military job specialty they performed. See 38 U.S.C. § 1116(d)(2). Here, the Veteran had service in Thailand from June 1969 to June 1970 and from June 1974 to June 1975. The Board is bound by these favorable findings. 38 C.F.R. § 3.104. The issue on appeal is whether the Veteran's colon cancer was caused by service, to include his exposure to herbicide agents and toxic exposure risk activities (TERA). However, the Board finds that the evidence of record is insufficient to make a fully-informed decision on the issue. The Board concludes that remand is necessary to correct a pre-decisional duty to assist error and to obtain an adequate VA medical opinion. The August 2023 VA medical opinion concluded that the Veteran's colon cancer was less likely than not related to toxic exposure. The rationale focused primarily on the lack of medical literature linking herbicide exposure to colon cancer and the absence of colon cancer among the diseases presumed to be associated with such exposure. The examiner referenced the Veteran's service in Thailand and MOS but did not analyze his specific exposure history, the cumulative nature of potential toxicants encountered during service, or provide any discussion of his lay contentions regarding environmental conditions. See August 2023 VA Medical Opinion. The examiner also did not analyze the synergistic or cumulative effect of multiple toxicants. The record reflects that the Veteran served as an operating room technician and tactical aircraft maintenance technician - roles which often involve exposure to sterilizing agents, solvents, jet fuel, and maintenance chemicals. VA conceded TERA participation and exposure to herbicide agents, to include TCDD, yet the examiner did not explain how this exposure profile may (or may not) relate to the etiology of the Veteran's colon cancer. Additional development remains necessary to adequately identify and evaluate the Veteran's potential exposure risks, particularly as related to his MOS and locations of service. Additionally, the Veteran testified that during service, he lived in barracks where beds were not provided, and monthly chemical spraying occurred to control insects. He stated that he recognized the spray by its distinctive smell and associated these environmental exposures during service. See January 2025 Hearing Transcript. This lay evidence raises the possibility of pesticide exposure, which has not been adequately considered by any VA examiner. While the August 2023 VA examiner stated that some pesticides have been linked to an increased risk of colon cancer, they did not address whether it contributed to the Veteran's colon cancer, particularly when considered cumulatively with his other occupational and environmental risks on top of his exposure to herbicide agents. Although the examiner stated that data on an association between herbicide agents and colon cancer was not prevalent in the medical literature, it is important to note that the scarcity of data does not necessarily indicate the absence of risk, which underscores the need for further development in this case. See Horn v. Shinseki, 25 Vet. App. 231, 239 (2012) (observing that the absence of evidence is not substantive negative evidence). Finally, the examiner did not address latency. Colon cancer often develops over many years. No rationale was provided to reconcile the delayed onset with service exposures from the 1960s and 1970s. An opinion that omits such medical reasoning cannot be deemed adequate. See Nieves-Rodriguez v. Peake, 22 Vet. App. 295, 301 (2008); Stefl v. Nicholson, 21 Vet. App. 120, 124 (2007). In sum, the record establishes that the Veteran was exposed to toxic chemicals during verified periods of service, has a current diagnosis of colon cancer, and has raised a plausible theory of entitlement based on lay testimony and occupational risk. Therefore, the absence of an adequately responsive medical opinion in the claims file amounts to a pre-decisional duty to assist error that must be corrected. 38 C.F.R. § 20.802(a). To this end, entitlement to service connection for colon cancer is remanded. The matters are REMANDED for the following action: 1. Prepare a full ILER. Identify specific toxic exposures to which the Veteran was potentially exposed, based on his MOS and duty locations. If more detail is needed, contact the Veteran to request the information. If there is still insufficient information to verify specific toxic exposure, provide the Veteran with written notice of that fact and outline the steps taken to assist. 2. Obtain a medical opinion from an appropriate clinician to address the nature and etiology of the Veteran's colon cancer. The clinician must review the claims file and provide a response to the following: (a.) Is the Veteran's colon cancer related to service, including the indicated toxic exposure risk activities (TERAs)? In providing the requested opinion, the clinician must consider the total potential exposure through all of the Veteran's applicable military deployments and the synergistic, combined effect of all TERAs. Cory M. Picton Veterans Law Judge Board of Veterans' Appeals Attorney for the Board R. Skinner The Board's decision in this case is binding only with respect to the instant matter decided. This decision is not precedential and does not establish VA policies or interpretations of general applicability. 38 C.F.R. § 20.1303.